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S

Sabot

Lightweight carrier to permit firing a smaller projectile from a larger weapon having a larger bore.

Safe And Arm

A device for interrupting (safing) and aligning (arming) an explosive train.

Safety Fuse

A flexible cord containing an internal burning medium by which fire or flame is conveyed at a continuous and uniform rate from the point of ignition to the point of use, usually a fuse detonator.

Safety Standard

Suggested precautions relative to the safety practices to be employed in the manufacture, transportation, storage, handling, and use of explosive materials.

Safety Wire

Wire set into the body of a fuze to lock all movable parts into safe position so that the fuze will not be set off accidentally. It is pulled out just before loading.

Salt

A chemical compound (other than water) formed by neutralization reactions between Acids and Bases; by direct combination of metal with nonmetal, e.g., sodium chloride (common table salt); by reaction of a metal with a dilute acid; by reaction of a metal oxide with acid; by reaction of a nonmetallic oxide with a base; or by reaction of two salts with each other to form two new salts. Most salts are ionic compounds. The chemical formula indicates the proportion of atoms of the elements making up the salt. A salt is classified as acidic, basic, or normal if it has, respectively, hydrogen (H), hydroxyl (OH), or neither in its formula. A salt undergoes dissociation when dissolved in a polar solvent, e.g., water

Saltpeter

Saltpeter or potassium nitrate, chemical compound (KNO₃), occurring as colorless prismatic crystals or as a white powder. When heated, it decomposes to release oxygen. Saltpeter has been used in gunpowder manufacture since about the 12th century, it is also used in explosives, fireworks, matches, and fertilizers, and as a food preservative.

Sample

That fraction of the population that is to undergo testing. Something to be analyzed.

Sapper

Soldier in WWI who was tasked with demolishing battle field barriers.

Satellite, artificial

An object launched by a Rocket into orbit around the earth or, occasionally, another solar-system body ( Space Probe). A satellite in circular orbit at an altitude of 22,300 mi (35,880 km) has a period of exactly 24 hr, the time it takes the earth to rotate once on its axis; such an orbit is called synchronous. If such an orbit also lies in the equatorial plane, it is called geostationary, because the satellite will remain stationary over one point on the earth's surface. The first artificial satellite, Sputnik 1, was launched by the USSR on Oct. 4, 1957. Explorer 1, the first American satellite, was launched on Jan. 31, 1958. The principal types of applications satellites are Communications Satellites, Navigation Satellites, Reconnaissance Satellites and Weather Satellites. Major U.S. scientific research satellites include the Orbiting Astronomical Observatories (OAO), the Orbiting Geophysical Observatories (OGO), the Orbiting Solar Observatories (OSO), the High Energy Astronomical Observatories (HEAO), many Explorer satellites, the Solar Maximum Mission (SMM), and the forthcoming Space Telescope. Major Soviet space-science satellite programs include Elektron, Proton, Prognoz, and many Cosmos satellites. The U.S. has also launched several Landsat satellites to survey the earth's resources by means of special television cameras and radiometric scanners.

Satellite, natural

A celestial body orbiting a planet. The earth's only satellite is the MOON; thus satellites of other planets are often referred to as moons. The largest in the solar system is Jupiter's Ganymede, whose radius of 1,639 mi (2,638 km) is larger than that of the planet Mercury. Also Planet, table; articles on individual planets.

Scabbing

Breaking off of fragments from the inside wall of hard material due to impact or explosion of a projectile on the outside. Spall.

Scaled Distance

A factor relating similar blast effects from various size charges of the same explosive at various distances. Scaled distance referring to blasting effects is obtained by dividing the distance of concern by a fractional power of the weight of the explosive materials.

Scaling Law

A formula which permits calculating some explosive effect based on data obtained from a similar but different size article.

Scavenger

Sometimes used to indicate removal of (gaseous) material by energetic chemical action.

SCID (Small Column Insulated Delay)

Slow burning pyrotechnic core contained in a flexible metallic sheath used to produce delay trains.

Screening Smoke

Chemical agent which, when burned, hydrolyzed or atomized produces an obscuring smoke; used to deny observation and reduce effectiveness of aimed fire.

Second

Second (sec or s), fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute and 1/3,600 of an hour. Since 1967 it has been calculated by atomic standards to be 9,192,631,770 periods of vibration of the radiation emitted at a specific wavelength by a cesium-133 atom.

Secondary Explosive

A high explosive which is relatively insensitive to heat and shock, usually initiated by a primary explosive or by an exploding bridgewire.

Secondary Fragmentation

Fragments produced by an explosive device that are made up of the target materials or other materials other than those directly resulting from the device itself.

Seek / Seeker

Refers to instrumentation for the guiding of missiles to the target.

Seismograph

An instrument, useful in monitoring blasting operations, that records ground vibration. Particle velocity, displacement, or acceleration is generally measured and recorded in three mutually perpendicular directions.

Semiconductor

Semiconductor, a solid material ( Solid State Physics) whose electrical conductivity at room temperature lies between that of a conductor and that of an insulator ( Conduction; Insulation). At high temperatures its conductivity approaches that of a metal, and at low temperatures it acts as an insulator. In a semiconductor there is a limited movement of electrons, depending upon the crystal structure of the material used. Incorporation of certain impurities in a semiconductor enhances its conductive properties. The impurities either add free electrons or create holes (electron deficiencies) in the crystal structures of the host substances by attracting electrons. Thus there are two semiconductor types: the n-type (negative), in which the current carriers (electrons) are negative, and the p-type (positive), in which the positively charged holes move and carry the current. Compounds such as indium antimonide, gallium arsenide, and aluminum phosphide are semiconductors. Semiconductors are used in electronic devices such as computers, Photoelectric Cells, Rectifiers, and Transistors.

Semifixed Ammunition

Ammunition in which the cartridge case is not permanently fixed to the projectile, so that the zoned charge within the cartridge case can be adjusted to obtain the desired range; loaded into the weapon as a unit.

Semifixed Round

Round of semifixed ammunition.

Semtex

Trade name of a plastic explosive ( Plastic Bonded Explosives) from the Czechoslovakian firm Synthesia, Pardubice-Semtin.

Semtex consists of Pentaerythritol Tetranitrate and styrene-butadiene copolymer as a plasticizer.

detonation rate: 5000 m/s

oxygen balance: -44.0%

critical diameter: 15 mm

Sensitiveness

A measure of an explosive’s cartridge-to-cartridge propagating ability under certain test conditions. It is expressed as the distance through air at which a primed half-cartridge (donor) will detonate an unprimed half-cartridge (receptor).

Sensitivity

A physical characteristic of an explosive material classifying its ability to be initiated upon receiving an external impulse such as impact, shock, flame, friction, or other influences that can cause explosive decomposition.

Separated Ammunition

Separated ammunition is characterized by the arrangement of the propelling charge and the projectile for loading into the gun. The propelling charge, contained in a primed cartridge case that is sealed with a closing plug and the projectile are loaded into the gun in one operation. Separated ammunition is used when the ammunition is too large to handle as fixed ammunition.

Separate-Loading Ammunition

Ammunition in which the projectile, propelling charge and primer are not held together in a shell case, as in fixed ammunition, but are loaded into a gun separately. No cartridge case is utilized in this type of ammunition.

Separating Burst

Method of ejecting the contents of a projectile by means of a charge of propellant that breaks the projectile into two approximately equal parts, along a specially designed circumferential shear joint.

Separation Distances

Minimum recommended distances from explosive materials accumulations to certain specific locations.

Series Blasting Circuit

An electric blasting circuit that provides one continuous path for the current through all caps in the circuit.

Series in Parallel Blasting Circuit

An electric blasting circuit in which the ends of two or more series of electric detonators are connected across the firing line directly or through buswire.

Service Ammunition

Ammunition intended for combat rather than for training purposes.

Setback

Rearward movement of components of a missile, relative to the missile as a whole, that results from the force due to acceleration during launching.

Shaped Charge

An explosive charge with a lined cavity specifically designed to produce a high velocity cutting or piercing jet of liner material. Mohaupt Effect.

Sheet Explosive

Known by many trade names, such as Metabel, Deta sheet, Series 1000 - PETN sheet explosive, and Series 2000 - RDX sheet explosive. These plastic bonded explosives have a very high brisance and detonating velocity. Sheet explosive is in most cases the explosive of choice for the tactical loading of the HYDRO CUT Entry and Gun Port Frames. Sheet explosive is supplied in North America in rolls which are a standard 10” wide. Depending on the thickness of the sheet explosive it is supplied as two X 10 pound rolls per box, or two X 20 pound rolls per box. P.E.T.N. - SERIES 1000 SHEET EXPLOSIVE PRODUCT INFORMATION

63% PETN, V.O.D. 6800 m/s, Density 1.48 g/cc

THICKNESS IN INCHES WEIGHT (Gm/Sq. INCH) LENGTH IN FEET/ROLL WEIGHT IN POUNDS/ROLL PETN BASED

0.042 C-1.0 36 10 *

0.062 C-1.5 24 10 *

0.083 C-2.0 36 20 *

0.125 C-3.0 24 20 *

0.166 C-4.0 18 20 *

0.208 C-5.0 15 20 *

0.250 C-6.0 12 20 *

0.333 C-8.0 9 20 *

R.D.X. - SERIES 2000 SHEET EXPLOSIVE PRODUCT INFORMATION
88% RDX, V.O.D. 7800 m/s, Density 1.58 g/cc

THICKNESS IN INCHES WEIGHT (Gm/Sq. INCH) LENGTH IN FEET/ROLL WEIGHT IN POUNDS/ROLL RDX BASED

0.083 C-2.0 33 20 *

0.125 C-3.0 22 20 *

0.166 C-4.0 18 20 *

0.250 C-6.0 11 20 *

0.300 C-8.0 9 20 *

Sheet explosive should be cut with a knife, not with scissors or shears to avoid potential injury. Both Series 1000 and Series 2000 are cap sensitive explosives.

Shelf Life

The length of time of storage during which an explosive material retains adequate performance characteristics.

The storage time during which an explosive item remains serviceable.

Shell

Hollow projectile filled with explosive, or chemical or other material as opposed to shot, which is a solid projectile.

Shell-Destroying Tracer

Tracer with an igniter element, placed between the explosive in an antiaircraft projectile and the tracer element, that is designed to detonate the explosive after the projectile has passed the target point but is still high enough to be harmless to ground troops.

Shock Wave

Rapid expansion of hot gases resulting from detonation of an explosive charge. A shock wave is a wave formed of a zone of extremely high pressure within a fluid ( Fluid Mechanics), especially one such as the atmosphere, that propagates through the fluid at supersonic speed, i.e., faster than the speed of Sound. Shock waves are caused by the sudden, violent disturbance of a fluid, such as that created by a powerful explosion or by the supersonic flow of a fluid over a solid object ( Sonic Boom). Shock Wave

A transient pressure pulse that propagates at supersonic velocity. Shock Tube add description

Nonel

Short-Delay Blasting

The practice of detonating blastholes in successive intervals where the time difference between any two successive detonations is measured in milliseconds.

Short Delay Fuze

One which will burst a projectile on ricochet, preferably about 6 to 10 feet above ground. Some crater effect will be obtained on hard ground.

Shot

I.) A solid projectile for cannon, without a bursting charge.

2.) Pellets; small balls, or slugs in shotgun shells, and some other types of ammunition.

Shot Firer

That qualified person in charge of and responsible for the loading and firing of a blast ( Blaster).

Shrapnel

Artillery projectile which contains small lead balls that are propelled by a powder charge in the base, set off by a time fuze. Shrapnel has been replaced almost entirely by high-explosive shells. Wounds called shrapnel wounds usually are due to shell fragments rather than to shrapnel.

Shrinkage

Contraction of propellant grain from wet (green) dimensions (as it comes from the graining dye) to the dry dimensions after solvent extraction and evaporation.

Shunt

The shorting together of the free ends of 1) electric detonator legwires, or 2) the wire ends of an electric blasting circuit or part thereof; the name of an electrical shorting device applied to the free ends of electric detonators by the manufacturer.

SI System Of Measurement

SI, which is the abbreviation of the French word “Systeme Internationale d’Unites”, is the accepted abbreviation for the International Metric System, which has several base units, as shown below.

Quantity measured Unit Abbreviation

Length meter m

Mass kilogram kg

Time second s

Electrical Current ampere A

Temperature degree Kelvin K

Luminous Intensity candela cd

Amount Of Substance mole mol

Side Spray

Spray.

Signal

A pyrotechnic item designed to produce a sign (illumination, smoke or sound) to provide identification, location, warning, etc.

Signaling Smoke

Any type of smoke, but usually colored smoke from a hand or rifle grenade, or from a message.

Signs-Explosive (Placards)

Signs, called placards, placed on vehicles transporting explosives denoting the character of the cargo, or signs placed near storage areas as a warning to unauthorized personnel.

Silica

A compound of silicon such as quartz sand.

Silicon

A chemical element used in pyrotechnics.

Silicone

A modern type of plastic.

Silver Chloride Cell

A special battery of relatively low current output used in a blasting galvanometer.

Simple Harmonic Motion

Simple harmonic motion is the relationship between displacement, frequency and velocity allowing calculation of any of the three if the other two are known.

V = 2 p f D where:

V = peak particle velocity in inches per second (ips)

p = 3.14

f = frequency in Hertz (cycles per second)

D = maximum displacement (inches)

also T = period = 1/f

and 2 p f = the circular frequency of the particle, = (or angular velocity)

Hence, D = V / 2 p f and f = V / 2 p D

Simulator

An item which simulates a hazardous item for training purposes, also a type of test instrument.

Single-Base Propellant

Propellant whose principal active ingredient is nitrocellulose.

Single-Section Charge

Propelling charge in separate-loading ammunition that is loaded into a single bag. A single-section charge cannot be reduced or increased for changes of range, as a multi-section charge can be.

Slurry

An aqueous explosive material solution of AN sensitized with a combustible fuel (and thickened with a gelling agent at the point of charging).

SMDC (Shielded Mild Detonating Cord)

MDF contained in a small (.180" diameter) steel tubing. Sometimes referred to as hardline CDF.

Small Arms

Small arms, firearms designed primarily to be carried and fired by one person, as distinguished from heavy arms, or Artillery, from which such weapons developed in the late 1300s. At first, small arms were nothing more than small, hand-held cannon fired by placing a small flame at the touchhole. In the matchlock—the first real handgun—a trigger moved the flame to the touchhole; in its successors, the wheel lock and flintlock, a spark-producing mechanism ignited the Gunpowder. Among early weapons of this kind were the musket, fired from the shoulder, and the pistol, held and fired with one hand. The rifle, invented in the 15th cent., is a firearm with a rifled bore (that is, with spiral grooves that impart a spinning motion to the bullet, giving it greater accuracy). Rifles first came into widespread use in the American colonies. Two major innovations of the early 19th cent. were the percussion cap, a small capsule filled with fulminate of mercury that exploded when struck and fired the gun instantly; and the gas-expanding bullet, which, after being dropped down the barrel of a rifle, would expand when fired to fit the barrel's rifling. Both sides in the U.S. Civil War used a rifled musket. Thereafter, all guns became rifled with the exception of the shotgun, a smooth-bored, short-range gun firing a single slug or several small shot. Practical breech-loading, or rear-loading, firearms came into general use about 1870; by the 1880s magazine loading, smokeless powder, and bolt action had been introduced. Although a crude “revolving pistol” existed in the late 16th cent., the modern revolver was introduced c.1835 by Samuel Colt. Colt's revolving cylinder permitted his gun to be fired six times without reloading. The revolver and the magazine-loading rifle were the standard small arms of the later 19th cent., but around 1900 a host of new automatic weapons were developed. The heavy Gatling gun, used in the U.S. Civil War, was the forerunner of the modern, rapid-firing machine gun, which achieved its full potential during the trench warfare of World War I and remains an important military firearm. The 1920s saw the development of submachine guns, notably the Thompson submachine gun (or “tommy gun”), an easily portable automatic weapon that fired 450 to 600 cartridges per minute. During World War II the bolt-action rifle was supplanted by the semiautomatic Garand rifle—a lightweight, self-loading, clip-fed shoulder weapon. The Garand was the standard U.S. army and marine corps service rifle through the time of the Korean War. The American-made M-16 rifle, still widely used, can fire accurately up to 500 yd (460 m) when hand-held and up to 800 yd (730 m) when mounted.

Small-Arms Ammunition

Any cartridge for shotgun, rifle, pistol, revolver, and cartridges for propellant-actuated power devices and industrial guns. Military-type ammunition containing explosive bursting charges or any incendiary, tracer, spotting, or pyrotechnic projectile is excluded from this definition.

Small-Arms Ammunition Primers

Small percussion-sensitive explosive charges encased in a cap or capsule and used to ignite propellant powder.

Smoke

The airborne suspension of solid particles from the products of detonation or deflagration.

Smoke Shell

Any projectile containing a smoke-producing chemical agent that is released on impact or burst. Also called smoke projectile. Smoke may be white or colored. Colored Marker Shell.

Smokeless Propellant (Smokeless Powder)

Solid propellant, commonly called smokeless powder in the trade, used in small-arms ammunition, cannon, rockets, propellant-actuated power devices, etc.

Smokeless Powder

Smokeless Propellant.

Smooth-Bore

Having a bore that is smooth and without rifling; shotguns and mortars are commonly smooth-bore

SN

Sodium nitrate.

Sodium

Sodium (Na), metallic element, discovered in 1807 by Sir Humphrey Davy; its compounds have been known since antiquity. A silver-white, very reactive Alkali Metal, it must be stored out of contact with air and water. The metal is used in arc-lamp lighting, as a heat-transfer liquid in nuclear reactors, and in manufacture of tetraethyl lead. Widely used compounds include Sodium Chloride (common salt), Sodium Bicarbonate (baking soda), Sodium Carbonate (soda ash), hydroxide (lye), nitrate, phosphates, and Borax. Soap is made with sodium hydroxide. Sodium compounds are widely distributed in rocks, soil, oceans, salt lakes, mineral waters, and salt deposits, and are found in the tissues of plants and animals. Sodium is an essential element of the diet. Element;Periodic Table.

Sodium Bicarbonate

Or sodium hydrogen carbonate, chemical compound (NaHCO₃), a white crystalline or granular powder, commonly known as bicarbonate of soda or baking soda. It is soluble in water and very slightly soluble in alcohol. Because it evolves carbon dioxide gas when heated above 50�C (122� F), it is used in baking powder. It is sometimes used medically to correct excess stomach acidity.

Sodium Carbonate

A chemical compound (Na₂CO₃) soluble in water and very slightly soluble in alcohol. Pure sodium carbonate is a white, odorless powder that absorbs moisture from the air and forms a strongly alkaline water solution. One of the most basic industrial chemicals, it is usually produced by the Solvay process. The chief uses of sodium carbonate are in glassmaking and the production of chemicals.

Sodium Chloride

(NaCl), common salt. It is a chemical compound containing equal numbers of positively charged sodium and negatively charged chlorine Ions. The colorless-to-white crystals have no odor but a characteristic taste. When dissolved in water, the ions move about freely and conduct electricity ( Electrolysis). Salt is essential in the diet of humans and animals, and is a part of blood, sweat, and tears. Salt is widely used for the seasoning, curing, and preserving of foods. Its major use is in the production of Chlorine, Sodium, and Sodium Hydroxide. Salt makes up nearly 80% of the dissolved material in seawater and is also widely distributed in solid deposits. Manufacture and use of salt is one of the oldest chemical industries.

Sodium Tetraborate

Decahydrate, Borax or chemical compound (Na₂B₄O₇• 10H₂O) occurring as a colorless, crystalline salt or a white powder. Borax is used as an antiseptic, cleansing agent, water softener, corrosion inhibitor in anti freeze, and flux for silver soldering, and in the manufacture of fertilizers, Pyrex glass, and pharmaceuticals.

Sofar Bomb

A sound producing bomb designed to detonate at a given depth under water.

Solar Energy

Any form of Energy radiated by the Sun, including light, radio waves, and X rays. Solar energy is needed by green plants for the process of Photosynthesis, which is the ultimate source of all food. The energy in fossil fuels (e.g., coal and petroleum) and other organic fuels (e.g., wood) is derived from solar energy. Difficulties with these fuels have led to the invention of devices that directly convert solar energy into usable forms of energy, such as electricity. Solar batteries, which operate on the principle that light falling on photosensitive substances causes a flow of electricity, play an important part in astronautics but are presently too expensive to be in common use on the earth ( Photovoltaic Cell). Thermoelectric generators convert the heat generated by solar energy directly into electricity. Heat from the sun is used in air-drying a variety of materials and in producing salt by the evaporation of sea water ( Desalination). Experimental solar heating systems can supply heat and hot water for domestic use; heat collected in special plates on the roof of a house is stored in rocks or water held in a large container. Such systems, however, usually require a conventional heater to supplement them. Solar stoves, which focus the sun's heat directly, are employed in regions where there is perennial sunlight.

Solar system

The Sun and the family of Planets, natural Satellites, Asteroids, Meteors, and Comets; in order of increasing distance from the sun, they are MERCURY, VENUS, EARTH, MARS, JUPITER, SATURN, URANUS, NEPTUNE, and PLUTO. All the planets orbit the sun in approximately the same plane (that of the ECLIPTIC) and move in the same direction (from west to east). Current theories suggest that the solar system was formed from a NEBULA consisting of a dense nucleus, or protosun, surrounded by a thin shell of a gaseous matter extending to the present edges of the solar system. Because of gravitational instabilities, the nebula eventually broke up into whirlpools of gas, called protoplanets, within the rotating mass. In time the protoplanets condensed and accreted to form the planets.

Major Planets Of The Solar System
Planet Distance from the sun (AU)* Period of revolution Period of rotation Mass (earth = l) Diameter (earth = l) Known Satellites

Mercury 0.39 88 days 59 days 0.06 0.38 0

Venus 0.72 225 days 243 days 0.82 0.95 0

Earth 1 365 days 24 hours 1 1 1

Mars 1.52 687 days 25 hours 0.11 0.53 2

Jupiter 5.20 12 years 10 hours 317.89 11.27 16

Saturn 9.54 29 years 10 hours 95.15 9.44 17

Uranus 19.18 84 years 16 hours 14.54 4.10 15

Neptune 30.06 165 years 18 hours 17.23 3.88 8

Pluto 39.44 248 years 6.4 days .002? 0.12-0.30 1

* AU = AstronAstromical Unit (Earth = 1)

Solar Time

Time defined by the position of the sun. The observer's local solar time is 0 hr (noon) when the center of the sun is on the observer's meridian. The solar day is the time it takes for the sun to return to the same meridian in the sky. The length of the solar day varies throughout the year because the earth moves with varying speed in its orbit and because the equatorial plane is inclined to the orbital plane. It is thus more convenient to define time in terms of the mean solar time, or average of local solar time; hence every mean solar day is of equal length. The equation of time is the difference between the local solar time and the mean solar time at a given location. Civil time is mean solar time plus 12 hr; the civil day begins at midnight, whereas the mean solar day begins at noon. Greenwich mean time (GMT) is the local civil time at the former site of the Royal Observatory in Greenwich, England, which is located on the Prime Meridian (0� longitude). Standard time is the civil time within one of the 24 time zones into which the earth's surface is divided. Within a zone all locations keep the same time, namely, the mean solar time of the central meridian (except when Daylight Saving Time is in effect). Zone times generally differ by a whole number of hours from GMT.

Solar Wind

A stream of ionized hydrogen and helium that radiates outward from the sun, carrying away about 1 million tons of gas per sec. Near the earth the solar wind normally has a velocity of 450 mi/sec (700 km/sec). The wind is believed to extend to between 100 and 200 astronomical units from the sun. Comet tails always point away from the sun because of the pressure exerted by the solar wind. The interaction of the solar wind with the earth's magnetic field is also responsible in part for such phenomena as the auroras and geomagnetic storms.

Solid Propellant

Specifically, a rocket propellant in solid form, usually containing both fuel and oxidizer combined or mixed and formed into a monolithic (not powdered or granulated) grain.

Solid-State Physics

Solid-state physics, the study of properties exhibited by atoms because of their association and regular, periodic arrangement in Crystals. Besides mechanical and thermal properties, electric conductivity ( Conduction) is one of the most important properties of solids. Metals are highly conductive and offer little resistance to electric currents. Most solid nonmetals are insulators; they offer virtually infinite resistance to electric currents. Semiconductors, which possess electrical conductivity that is neither very high nor very low, are used in Transistors.

Sonic boom

A sonic boom is a Shock Wave produced by an object moving through the air at supersonic speed, i.e., faster than the speed of sound. An object, such as an airplane, moving through the air generates sound. When the speed of the object exceeds the speed of sound, the object forces the sound ahead of itself faster than the speed at which the sound would ordinarily travel. The piled-up sound takes the form of a violent shock wave propagating behind the object.

Sound

Sound is pressure Waves that propagate through air or other media. Sounds are generally audible to the human ear if their frequency lies between 20 and 20,000 vibrations per second. Sound waves with frequencies below the audible range are called subsonic, and those with frequencies higher than the audible range are called ultrasonic ( Ultrasonics). When a body, such as a violin string, vibrates, or moves back and forth, its movement in one direction pushes the molecules of the air before it, crowding them together. When it moves back again past its original position and on to the other side, it leaves behind it a nearly empty space. The body thus causes alternately in a given space a crowding together of the air molecules (a condensation) and a thinning out of the molecules (a rarefaction). The condensation and rarefaction make up a sound wave; such a wave is called longitudinal, or compressional, because the vibratory motion is forward and backward along the direction that the wave is following. Because such a wave consists of a disturbance of particles of a material medium, sound waves cannot travel through a vacuum. The velocity of sound in air at 32�F (0�C) is 1,089 ft/sec (331.9 m/sec), but at 68�F (20�C) it is increased to about 1,130 ft/sec (344.4 m/sec). Sound travels more slowly in gases than in liquids, and more slowly in liquids than in solids. The pitch of a sound depends upon the frequency of vibration; the higher the frequency, the higher the pitch. Loudness, or intensity of sound, is measured in units called Decibels. Also Accoustics; Doppler Effect; Echo; Interference.

Sound Speed

A materials sound speed is the rate at which sound is conducted through that particular medium. A materials sound speed is also effected by the temperature the particular material is at. For example at standard temperature and standard pressure (STP) the velocity of sound in air is 340 m/s, (331 m/s at 0� C). The density of air at STP is 1.39 kg/m³. In air or other gases, the velocity of sound increases proportionally with the square root of the absolute temperature; the velocity increase is approximately 2% for each 10� C temperature increase. Usually, the temperature decreases with altitude - an average of the gradient is 0.6� C per 100 meters.

Space-Time

Space-time, the central concept in the theory of Relativitythat replaces the earlier concepts of space and time as separate absolute entities. In space-time, events in the universe are described in terms of a four-dimensional continuum in which each observer locates an event by three spacelike coordinates and a timelike coordinate. The choice of the last is not unique; hence, time is not absolute but is relative to the observer.

Spall

Fragments broken from either surface of a barrier (for example, fragments broken from an armor plate as the result of penetration, impact of a projectile, or detonation against the plate.

Specific Density

Mass per unit volume of a homogeneous material. In interior ballistics, it is usually distinguished from loading density and gravimetric density.

Specific Energy

The specific energy of an explosive is defined as its working performance per kg, calculated theoretically from the general equation of state for gases:

f = pV = nRT

where p is the pressure, V is the volume, n is the number of moles of the explosion gases per kg ( � also Volume of Detonation gases), R is the ideal gas constant, and T is the absolute temperature of the explosion. If we put the volume equal to unity, i.e., if the loading density is unity, the specific energy becomes

f = p

i.e., is equal to the pressure which would be exerted by the compressed explosion gases in their confinement, if the latter were indestructible. This is why the term “specific pressure” is also frequently used, and why the magnitude f is often quoted in atmospheres.

Nevertheless, strictly speaking, [is an energy value and for this reason is reported in meter-tons per kg. The value of twill have this dimension if R is taken as 0.8479 � 10^-3mt � K � mol.

In accordance with recent standardization regulations, the energy data are also reported in joules. For more details Strength.

Specific Gravity

The ratio of the Weight of any volume of substance to the weight of an equal volume of pure water, which has a density of 1000 kg/m³ or can also be expressed as 1.00 g/cm³. Density.

Specific Heat

Specific heat is the ratio of the Heat Capacity of a substance to the heat capacity of a reference substance, usually water. Because the heat capacity of water is 1 BTU/Lb per degree Fahrenheit or 1 cal/gram per degree Celsius, the specific heat of a substance relative to water will be numerically equal to its heat capacity.

Specific Impulse

The thrust in pounds developed by burning one pound of a particular propellant in one second.

Spectrum

The arrangement or display of Light or other forms of Electromagnetic Radiation separated according to wavelength, frequency, energy, or some other property. Dispersion, the separation of visible light into a spectrum, may be accomplished by means of a prism or a Diffractiongrating. Each different wavelength or frequency of visible light corresponds to a different color, so that the spectrum appears as a band of colors ranging from violet at the short-wave length (high-frequency) end of the spectrum through indigo, blue, green, yellow, and orange, to red at the long-wavelength (low-frequency) end of the spectrum. A continuous spectrum containing all colors is produced by all incandescent solids and liquids and by gases under high pressure. A low-pressure gas made incandescent by heat or by an electric discharge emits a spectrum of bright emission lines. A dark-line absorption spectrum is produced by white light passing through a cool gas and consists of a continuous spectrum with superimposed dark lines; each line corresponds to a frequency where a bright line would appear if the gas were incandescent. The absorption lines correspond to transitions of electrons from a lower energy level to a higher energy level when a Photon is absorbed by the atom, and the emission lines correspond to transitions from a higher to a lower energy level in the atom, accompanied by the emission of a photon. The frequency of each emission or absorption line is proportional to the difference in energy between the two energy levels involved ( Quantum Theory). Both absorption and line spectra are useful in chemical analysis, because they reveal the presence of particular elements.

Spin
Angular velocity about the axis of the projectile.

Spin-Decelerating Moment

A couple about the axis of the projectile which diminishes spin.

Spin Stabilization

Method of stabilizing a projectile during flight by causing it to rotate about its own longitudinal axis.

Spray

Fragments of a bursting shell. The nose, side and base sprays are the fragments thrown forward, sideways and rearward, respectively.

Squashed-Head Shell

High Explosive Plastic Shell. Squib

Used as a general term to mean any of various small-size pyrotechnic or explosive devices.

Squib

A firing device that burns with a flash and is used for igniting black powder or pellet powder.

Squib Switch (Explosive Switch)

An electric switch operated by a squib or pressure cartridge. Stability

The ability of an explosive material to retain its original properties without degradation when exposed to various environmental conditions over a period of time.

Stability

The ability of an explosive material to retain chemical and physical properties specified by the manufacturer when exposed to specific environmental conditions over a particular period of time.

Stability Test

Accelerated test to determine the suitability of an explosive material for long-term storage under a variety of environmental conditions.

Stabilizer

Material added to propellant colloid to inhibit, or reduce, decomposition in storage.

Stacked Charge

Powder charge in which the powder grains lie end to end within the powder bag.

Staging Area

The area directly outside of the target area, the final location where the assault element will prepare to enter the target area.

Standard Atmosphere

Values of air temperature, pressure and density vs. altitude based on average conditions and arbitrarily assumed as standard for computations. Various standards are in current use.

Standard Deviation (Sigma)

The square root of the sum of the squared deviations from the mean. For a given sample, this must be divided by the sample size in order to correct for bias and be a proper estimate of the true population. A measure of the variability or dispersion of a number of observations.

Standard Trajectory

Calculated path that a projectile will follow under given conditions of weather, position and material, including the particular fuze, projectile and propelling charge that are used. Firing tables are based on standard trajectories.

Stand Off

The distance between a shaped charge liner and the target material.

Star (astrological)

Star, hot, incandescent sphere of gas (usually more than 90% hydrogen) that is held together by its own gravitation and emits light and other forms of electromagnetic radiation whose ultimate source is nuclear energy. The universe contains billions of galaxies, and each galaxy contains billions of stars, which are frequently bunched together in star clusters of as many as 100,000. The stars visible to the unaided eye are all in our own galaxy, the Milky Way. The visible stars are divided into six classes according to their apparent Magnitude. Stars differ widely in mass, size, temperature, age , and luminosity. About 90% of all stars have masses between one tenth and 50 times that of the sun. The most luminous stars (excluding supernovas) are about a million times more powerful than the sun, while the least luminous are only a hundredth as powerful. Variable stars fluctuate in luminosity. Red giants, the largest stars, are hundreds of times greater in size than the sun. At the opposite extreme, white dwarfs are no larger than the earth, and neutron stars are only a few kilometers in radius. The central region, or core, has a temperature of millions of degrees. At this temperature nuclear energy is released by the fusion of hydrogen to form helium. By the time nuclear energy reaches the surface of the star, it has been largely converted into visible light with a spectrum characteristic of a very hot body. The theory of stellar evolution states that a star must change as it consumes its hydrogen in the nuclear reactions that power it. When all its nuclear fuel is exhausted, the star dies, possibly in a supernova explosion.

Star (pyrotechnic)

Pyrotechnic signal that burns as a single light.

Star Gage

Instrument for measuring the diameter of the bore of a gun.

Star Grain

A solid propellant grain with an internal star-shaped cross section.

Star Shell

Illumination Shell.

Starting Mix

An easily ignited mixture that transmits flame from an initiating device to a less readily ignitable composition.

States Of Matter

The forms of matter differing in several properties because of differences in the motions of and the forces between the molecules (or atoms or ions) of which they are composed. There are three common states of matter: solid, liquid, and gas. The molecules of a solid are limited to vibrations about a fixed position, giving a solid both a definite volume and a definite shape. When heat is applied to a solid, its molecules begin to vibrate more rapidly until, at a temperature called the melting point, they break out of their fixed positions and the solid becomes a liquid. Because the molecules of a liquid are free to move throughout the liquid but are held from escaping by intermolecular forces ( Adhesion and Cohesion), a liquid has a definite volume but no definite shape. As more heat is added to the liquid, some molecules near the surface gain enough energy to evaporate, or break away completely from the liquid, and change to a gaseous state. Finally, at a temperature called the BOILING POINT, molecules throughout the liquid become energetic enough to escape, forming bubbles of vapor that rise to the surface; the liquid thus changes completely to a gas. Because its molecules are free to move in every possible way, a gas has neither a definite shape nor a definite volume but expands to fill any container in which it is placed. The reverse processes of melting and boiling are, respectively, freezing and condensation. Also Crystal; Gas Laws; Kinetic-Molecular Theory of Gases; Plasma..

Static Electricity

Electric charge at rest on a person or object. It is most often produced by the contact and separation of dissimilar insulating materials.

Static Entry

A description given to a type of entry where a team member has access to the target area, but is not moving into or around the target area, an example would be a gun port breach point.

Statics

Statics is a branch of Mechanics concerned with the maintenance of equilibrium in bodies by the interaction of Forces upon them. In a state of equilibrium the resultant of all outside forces acting on a body is zero, thus keeping the body at rest.

Statistical Method

A technique used to obtain, analyze and present numerical data.

Statistics

The science which deals with the collection, classification and use of numerical data relating to a given subject.

Steady State Velocity

The characteristic velocity at which a specific explosive at a given charge diameter will detonate.

Stemming

Material to be added.

Stoichiometric

Relating to components involved in a burning process which are present in exactly the quantities needed for reaction, without an excess of any component.

Storage

The safekeeping of explosive materials, usually in specially designed structures called magazines.

Stowage

1) Method of placing cargo in a vessel to prevent damage, shifting, etc.

2) Method of placing equipment and supplies in a vehicle to provide availability and operating room.

3) Equipment when stowed.

STP (Of Gases)

At standard temperature and pressure.

Stray Current

A flow of electricity outside an insulated conductor system.

Strength

The explosive strength of unit weight (or volume) of a high explosive when compared with that of Blasting Gelatine in a ballistic mortar. Although compared with Blasting Gelatine it is sometimes designated in percentage of nitroglycerine (%NG). This latter designation is not a true measure of its strength.

Strength of materials

Strength of materials, the capacity of materials to withstand stress (the internal force exerted by one part of an elastic body upon an adjoining part) and strain (the deformation or change in dimension occasioned by stress). When a body is subjected to a pull, it is said to be under tension, or tensional stress; when it is compressed, it is under compression, or compressive stress. Shear, or shearing stress, results when a force tends to make part of a body slide past the other part. Torsion, or torsional stress, occurs when external forces tend to twist a body around an axis. The elastic limit is the maximum stress that a material can sustain and still return to its original form. The ratio of tensile stress to strain for a given material is called its Young's modulus. Hooke's law states that, within the elastic limit, strain is proportional to stress.

Striker

Part of the firing mechanism of a gun, mine, mortar, etc., that hits the primer, hammer or firing pin of a gun.

Striking Velocity

Speed of a projectile at the point of impact.

Strontium

Strontium (Sr), metallic element, first recognized as distinct from barium by A. Crawford in 1790. A soft, silver-yellow Alkaline-Earth Metal, it is stored away from air and water. Strontium-90 from nuclear fallout is absorbed in plants and animals, and may induce bone cancer and leukemia. Element; Periodic Table.

Subcaliber

Of a caliber smaller than standard.

Subsonic

Less than the speed of sound of a particular medium.

Sulfur

Sulfur (S) or sulphur, nonmetallic element, known to antiquity as the biblical brimstone and recognized as an element by Antoine Lavoisier in 1777. Solid sulfur is yellow, brittle, odorless, tasteless, and insoluble in water. Sulfur is widely distributed in minerals and ores, some volcanic regions, and large underground deposits, and often occurs with coal, natural gas, and petroleum. It is found in most proteins and protoplasm of plants and animals. Sulfur is used in Gunpowder, matches, Rubber vulcanization, insecticides, and the treatment of certain skin diseases., Sulfuric Acid is its most important compound; others are used as disinfectants, refrigerants, organic solvents, and Sulfa Drugs. Element; Periodic Table.

Sun

Sun, intensely hot, self-luminous body of gases (mainly hydrogen and helium) at the center of the Solar System. The sun is a medium-size main-sequence Star. Its mean distance from the earth is defined as one Astronomical Unit. The sun is c.865,400 mi (1,392,000 km) in diameter; its volume is about 1,300,000 times, and its mass 332,000 times, that of the earth. At its center, the sun has a density over 100 times that of water, a pressure of over 1 billion atmospheres, and a temperature of about 15,000,000�K. This temperature is high enough for the occurrence of nuclear reactions, which are assumed to be the source of the sun's energy. Hans Bethe proposed a cycle of nuclear reactions known as the carbon cycle, in which carbon acts much as a catalyst, while hydrogen is transformed by a series of reactions into helium and large amounts of high-energy gamma radiation are released. The so-called proton-proton process is now thought to be a more important energy source: the collision of two protons ends with the production of helium atoms and the release throughout of gamma radiation. The bright surface of the sun is called the photosphere; its temperature is about 6000�K. During an Eclipse of the sun, the chromosphere (a layer of rarified gases above the photosphere) and the corona (a luminous envelope of extremely fine particles surrounding the sun, outside the chromosphere) are observed. Also Solar Wind; Sunspots.

Superconductivity

Superconductivity, the total disappearance of electrical resistance in a wire or circuit. Discovered in 1911, superconductivity only appears in a specific material below a critical temperature. The major problems confronting the possible applications of superconductivity were the extremely low temperatures initially required (only a few degrees above absolute zero) and the fact that a strong magnetic field could destroy it. Much research has been done in recent years in the field of “high-temperature” superconductivity. Newer composites permit the absence of electrical resistance at temperatures near 125� K (-243� F).

Superfluidity

The capability of liquid helium cooled below a temperature of 2.19�K (the lambda point) to flow freely, even upward, with no measurable friction and viscosity. Superfluid helium flows easily through capillary tubes ( Capillarity) that resist the flow of ordinary fluids, and a Dewar Flask filled with superfluid helium from a larger container will empty itself back into the original container because the liquid helium flows spontaneously in an invisible film over the surface of the flask.

Superquick Fuze

Fuze that functions immediately upon impact of the missile with the target. Action of this type of fuze is the quickest possible; the firing pin is driven into the primer immediately upon the first contact of the missile; functions at the surfaces of the target. Also called instantaneous fuze.

Supersensitive Fuze

Fuze that will set off a projectile when it strikes even a very light target, such as an airplane wing.

Supersonic

Greater than the speed of sound of a particular medium.

Supplemental Charge

Filler, normally TNT, used in deep cavitied projectiles to fill void between ordinary fuze and booster combination and bursting charge.

Sure-Fire Current

Minimum current which must be applied to a bridgewire circuit to reliably ignite the prime material without regard to the time of operation.

Surface tension

Surface tension, the cohesion forces ( Adhesion and Cohesion) at the surface of a liquid. The molecules within a liquid are attracted equally from all sides, but those near the surface experience unequal attractions and thus are drawn toward the center of the liquid mass by this net force. A result of surface tension is the tendency of a liquid to reduce its exposed surface to the smallest possible area.

Surveillance (as it pertains to ordnance)

Observation, inspection, investigation, test study and classification of ammunition, ammunition components and explosives in movement, storage and use with respect to degree of serviceability and rate of deterioration.

Sustainer Grain

A propellant or pyrotechnic grain used in a pressure cartridge or igniter to sustain burning.

Swell Diameter

Maximum diameter of the ogive extended to the place where its generating arc is parallel to the center line.

Switch

An electrical device having two states—on, or closed, and off, or open—and, ideally, having the property that when closed it offers a zero Impedance to a current and when open it offers infinite impedance to a current. For many operations, as in digital computers, the operation of mechanical switches, which move contacts together and apart, is too slow. When faster switching is required, Transistors or vacuum tubes are used, operated in such a way that they conduct either heavily or very little. Relay.

Sympathetic Detonation (Ignition)

The explosion of a second charge or device caused by nearby detonation (ignition) of another.

Sympathetic Propagation

The detonation of an explosive material as the result of receiving an impulse from another detonation through air, earth, or water.

Synthetic Elements

Synthetic elements, radioactive chemical elements discovered not in nature but as artificially produced isotopes. They are TECHNETIUM, PROMETHIUM, ASTATINE, FRANCIUM, and the TRANSURANIUM ELEMENTS. Some have since been found to exist in small amounts in nature as short-lived members of natural radioactive decay series ( Radioactivity).

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